title: 18 S rRNA degradation is not accompanied by altered rRNA transport at early times following irradiation of HeLa cells.
abstract: The effect of ionizing radiation (137Cs) on processing and transport of ribosomal RNA (rRNA) was studied by pulse-labeling HeLa S3 cells with [3H]uridine immediately prior to irradiation. This approach permits kinetic analysis of processing of 45 S rRNA (radiolabeled predominantly prior to irradiation) into its 28 S and 18 S rRNA daughter species following irradiation. By this technique, we have recently demonstrated an increase in the normal 28 S:18 S rRNA stoichiometric ratio of 1:1 to as high as 1.6:1 during the interval 5 to 20 h following irradiation of HeLa cells at greater than or equal to 7.5 Gy. Alterations in 28 S:18 S ratio were evaluated in greater detail at early times following irradiation, up to 2 h. The 28 S:18 S ratio was found to be maximal at 1 h after radiation, at about 2:1, following 5 or 10 Gy. Using a method for rapid separation of nucleus from cytoplasm, transport of rRNA from nucleus to cytoplasm was also evaluated during this period. Despite an increase in the rate of 45 S rRNA processing, as well as an increased 28 S:18 S ratio, no alterations in transport from nucleus to cytoplasm were detected. This lack of transport alteration suggests that accumulation of excess 28 S rRNA is restricted to the nucleus, where it may represent an early step in the process of radiation-induced cell killing.
authors.affiliation: Israel Institute for Biological Research, Ness-Ziona.
authors.forename: P
authors.initials: P
authors.lastname: Fuchs
authors.forename: J M
authors.initials: JM
authors.lastname: Krolak
authors.forename: D
authors.initials: D
authors.lastname: McClain
authors.forename: K W
authors.initials: KW
authors.lastname: Minton
mesh_terms: D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D002588:Cesium Radioisotopes; D003593:Cytoplasm / Q000378:metabolism; D005720:Gamma Rays; D006367:HeLa Cells / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D012335:RNA, Ribosomal / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D013997:Time Factors
chemical_list: D002588:Cesium Radioisotopes; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S